User guide

Level
The Level knob is the master volume control. It determines the amount of signal from the
preamplifier gain stage sent to the output stage. The cleanest signal is attained by setting the
Level knob between 7 and 10 on the scale, then turning the Gain knob until the desired level
is attained. Altering the Gain, Z-in Switch, and Output controls together provides many useful
tonal variations. The numeric values on the front panel for the Level control denote
magnatude and are NOT specific dB values. When the Level control is set to 10, the total
system gain will be the dB value selected by the Gain control.
Z-in Select
The Z-in push button switch provides two different input impedance choices for the Mic Input
and two different impedance choices for the Hi-Z Input.
The impedance for the MIC INPUT can be set to 1 KΩ or 4 KΩ. Pushing the Z-In Select button
in will select 1 KΩ When the button is out, 4 KΩ is selected.
Switching between these two positions while listening to a connected microphone may reveal a
different tonal quality and/or gain. A typical mic preamplifier should have an input impedance
equal to about 10 times the mic output impedance. For example, if your mic has an output
impedance between 150 Ω and 200 Ω, set the switch to the in position. However, since making
music is not necessarily about adhering to technical specifications, feel free to experiment with the
settings to attain the desired sound. You will not harm your microphone or the 2108.
The impedance for the Hi-Z INPUT can be set to 58 KΩ or 2 MΩ. Pushing this button in will
select 58 KΩ.When the button is out, 2 MΩ is selected.
The 58 KΩ setting is best suited for -10 dBv level signals, typically found on active basses
and guitars. This setting is also appropriate for devices with unbalanced line outs, such as
keyboards and drum machines. The 2 MΩ setting is appropriate for instruments with passive
pickup systems. Since an instrument’s output impedance may be somewhere between the
active and passive levels, feel free to experiment to achieve the best sound at the desired level.
Rev ø
The Rev ø push button reverses the polarity of the 2108 output when it is pushed in. When
pushed in pin 3 is hot (positive). When the button is out pin 2 is hot (positive).
+48 V (Phantom Power)
The +48V push button applies phantom power to the Mic Input XLR jack on the rear chassis.
Pushing this button in “turns on” the +48 volts. When the button is out, the +48 volts is off.
Most modern condenser mics require phantom voltage to operate and we recommend
checking the requirements of your microphones before connecting them. It is good practice to
keep phantom power off when it is not required. To avoid loud transients, always keep the
phantom power off when connecting or disconnecting microphones.
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